Process For Producing Polydienes

ABSTRACT

A process for preparing a polydiene, the process comprising the step of polymerizing conjugated diene monomer in the presence of a dihydrocarbyl ether, where said step of polymerizing takes place within a polymerization mixture that includes less than 20% by weight of organic solvent based on the total weight of the polymerization mixture, and where said step of polymerizing employs a lanthanide-based catalyst system that includes the combination of or reaction product of ingredients including (a) a lanthanide compound, (b) an aluminoxane, (c) an organoaluminum compound other than an aluminoxane, and (d) a bromine-containing compound selected from the group consisting of elemental bromine, bromine-containing mixed halogens, and organic bromides.

FIELD OF THE INVENTION

One or more embodiments of the present invention are directed toward aprocess for producing polydienes.

BACKGROUND OF THE INVENTION

Polydienes may be produced by solution polymerization, whereinconjugated diene monomer is polymerized in an inert solvent or diluent.The solvent serves to solubilize the reactants and products, to act as acarrier for the reactants and product, to aid in the transfer of theheat of polymerization, and to help in moderating the polymerizationrate. The solvent also allows easier stirring and transferring of thepolymerization mixture (also called cement), since the viscosity of thecement is decreased by the presence of the solvent. Nevertheless, thepresence of solvent presents a number of difficulties. The solvent mustbe separated from the polymer and then recycled for reuse or otherwisedisposed of as waste. The cost of recovering and recycling the solventadds greatly to the cost of the polymer being produced, and there isalways the risk that the recycled solvent after purification may stillretain some impurities that will poison the polymerization catalyst. Inaddition, some solvents such as aromatic hydrocarbons can raiseenvironmental concerns. Further, the purity of the polymer product maybe affected if there are difficulties in removing the solvent.

Polydienes may also be produced by bulk polymerization (also called masspolymerization), wherein conjugated diene monomer is polymerized in theabsence or substantial absence of any solvent, and, in effect, themonomer itself acts as a diluent. Since bulk polymerization isessentially solventless, there is less contamination risk, and theproduct separation is simplified. Bulk polymerization offers a number ofeconomic advantages including lower capital cost for new plant capacity,lower energy cost to operate, and fewer people to operate. Thesolventless feature also provides environmental advantages, withemissions and waste water pollution being reduced.

Despite its many advantages, bulk polymerization requires very carefultemperature control, and there is also the need for strong and elaboratestirring equipment since the viscosity of the polymerization mixture canbecome very high. In the absence of added diluent, the high cementviscosity and exotherm effects can make temperature control verydifficult. Consequently, local hot spots may occur, resulting indegradation, gelation, and/or discoloration of the polymer product. Inthe extreme case, uncontrolled acceleration of the polymerization ratecan lead to disastrous “runaway” reactions. To facilitate thetemperature control during bulk polymerization, it is desirable that acatalyst gives a reaction rate that is sufficiently fast for economicalreasons but is slow enough to allow for the removal of the heat from thepolymerization exotherm in order to ensure the process safety.

Lanthanide-based catalyst systems that comprise a lanthanide compound,an alkylating agent, and a halogen source are known to be useful forproducing conjugated diene polymers having high cis-1,4-linkagecontents. The resulting cis-1,4-polydienes typically have acis-1,4-linkage of less than 99%. Molecular weight distributions vary,but are typically above 2. It is known that cis-1,4-polydienes havinghigher cis contents, and narrower molecular weight distributions, give agreater ability to undergo strain-induced crystallization and lowerhysteresis and thus, give superior physical properties such as highertensile strength and higher abrasion resistance. Therefore, there is aneed to develop a process for producing cis-1,4-polydienes having acombination of ultra-high cis contents (greater than 99% cis) and narrowmolecular weight distributions.

Unfortunately, most catalyst systems can not consistently achieve all ofthese properties. For example, catalysts have been developed to producepolymers with cis-1,4-linkage contents above 99%, but have broadmolecular weight distributions. Furthermore, many of these catalysts usehighly active, Lewis acidic chlorides, bromides, and iodides to achievethese properties, which results in excessively fast polymerizationrates. This makes it very difficult to control the temperature andcompromises the process safety. Fast polymerization rates anduncontrollable temperatures often lead to gel formation inside thepolymerization reactor due to excess polymer formation on the walls ofthe reactor. In turn, the reactor must be cleaned before anotherpolymerization can be conducted resulting in expensive delays inproduction.

Therefore, it is desirable to develop a bulk polymerization method forproducing cis-1,4-polydienes having higher cis-1,4-linkage content andlower molecular weight distribution.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provide a process forpreparing a polydiene, the process comprising the step of polymerizingconjugated diene monomer in the presence of a dihydrocarbyl ether, wheresaid step of polymerizing takes place within a polymerization mixturethat includes less than 20% by weight of organic solvent based on thetotal weight of the polymerization mixture, and where said step ofpolymerizing employs a lanthanide-based catalyst system that includesthe combination of or reaction product of ingredients including (a) alanthanide compound, (b) an aluminoxane, (c) an organoaluminum compoundother than an aluminoxane, and (d) a bromine-containing compoundselected from the group consisting of elemental bromine,bromine-containing mixed halogens, and organic bromides.

Still other embodiments of the present invention provide a process forpreparing a polydiene, the process comprising the step of introducingconjugated diene monomer with a lanthanide-based catalyst system in thepresence of less than about 20% by weight organic solvent based on thetotal weight of the polymerization mixture, where the lanthanide-basedcatalyst system includes the combination of or reaction product ofingredients including (a) a lanthanide compound, (b) an aluminoxane, (c)an organoaluminum compound other than an aluminoxane, (d) abromine-containing compound selected from the group consisting ofelemental bromine, bromine-containing mixed halogens, and organicbromides, and (e) a dihydrocarbyl ether.

Still other embodiments of the present invention provide a process forpreparing a polydiene, the process comprising the step of introducing(a) a lanthanide compound, (b) an aluminoxane, (c) an organoaluminumcompound other than an aluminoxane, (d) a bromine-containing compoundselected from the group consisting of elemental bromine,bromine-containing mixed halogens, hydrogen bromide, and organicbromides, (e) a dihydrocarbyl ether, and (0 conjugated diene monomer,where said step of introducing forms a polymerization mixture thatincludes less than 20% by weight of solvent based on the total weight ofthe polymerization mixture.

Still other embodiments of the present invention provide acis-1,4-polydiene having a cis-1,4-linkage content of greater than 99%and a molecular weight distribution of less than 2.0.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

According to one or more embodiments of the present invention,polydienes are produced by bulk polymerization of conjugated dienemonomer with a lanthanide-based catalyst system that is the combinationof or reaction product of (a) a lanthanide compound, (b) an aluminoxane,(c) an organoaluminum compound other than an aluminoxane, (d) abromine-containing compound selected from the group consisting ofelemental bromine, bromine-containing mixed halogens, and organicbromides, and (e) a dihydrocarbyl ether. Without wishing to be bound byany particular theory, it is believed that these catalyst ingredientssynergistically yield a polydiene product with advantageous cis-1,4content and an overall balance of advantageous properties. Further, ithas been unexpectedly discovered that by including an iodine-containingcompound as an additional catalyst ingredient, the molecular weightdistribution can advantageously be improved without a deleterious impacton the other properties.

In one or more embodiments, examples of conjugated diene monomer thatcan be polymerized according to the present invention include1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene,2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene,2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,4-methyl-1,3-pentadiene, and 2,4-hexadiene. Mixtures of two or moreconjugated dienes may also be utilized in copolymerization.

Various lanthanide compounds or mixtures thereof can be employed. In oneor more embodiments, these compounds may be soluble in hydrocarbonsolvents such as aromatic hydrocarbons, aliphatic hydrocarbons, orcycloaliphatic hydrocarbons. In other embodiments, hydrocarbon-insolublelanthanide compounds, which can be suspended in the polymerizationmedium to form the catalytically active species, are also useful.

Lanthanide compounds may include at least one atom of lanthanum,neodymium, cerium, praseodymium, promethium, samarium, europium,gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium,lutetium, and didymium. Didymium may include a commercial mixture ofrare-earth elements obtained from monazite sand.

The lanthanide atom in the lanthanide compounds can be in variousoxidation states including but not limited to the 0, +2, +3, and +4oxidation states. Lanthanide compounds include, but are not limited to,lanthanide carboxylates, lanthanide organophosphates, lanthanideorganophosphonates, lanthanide organophosphinates, lanthanidecarbamates, lanthanide dithiocarbamates, lanthanide xanthates,lanthanide β-diketonates, lanthanide alkoxides or aryloxides, lanthanidepseudo-halides, and organolanthanide compounds.

Without wishing to limit the practice of the present invention, furtherdiscussion will focus on neodymium compounds, although those skilled inthe art will be able to select similar compounds that are based uponother lanthanide metals.

Neodymium carboxylates include neodymium formate, neodymium acetate,neodymium acrylate, neodymium methacrylate, neodymium valerate,neodymium gluconate, neodymium citrate, neodymium fumarate, neodymiumlactate, neodymium maleate, neodymium oxalate, neodymium2-ethylhexanoate, neodymium neodecanoate (a.k.a. neodymium versatate),neodymium naphthenate, neodymium stearate, neodymium oleate, neodymiumbenzoate, and neodymium picolinate.

Neodymium organophosphates include neodymium dibutyl phosphate,neodymium dipentyl phosphate, neodymium dihexyl phosphate, neodymiumdiheptyl phosphate, neodymium dioctyl phosphate, neodymiumbis(1-methylheptyl) phosphate, neodymium bis(2-ethylhexyl)phosphate,neodymium didecyl phosphate, neodymium didodecyl phosphate, neodymiumdioctadecyl phosphate, neodymium dioleyl phosphate, neodymium diphenylphosphate, neodymium bis(p-nonylphenyl) phosphate, neodymium butyl(2-ethylhexyl)phosphate, neodymium (1-methylheptyl)(2-ethylhexyl)phosphate, and neodymium (2-ethylhexyl)(p-nonylphenyl)phosphate.

Neodymium organophosphonates include neodymium butyl phosphonate,neodymium pentyl phosphonate, neodymium hexyl phosphonate, neodymiumheptyl phosphonate, neodymium octyl phosphonate, neodymium(1-methylheptyl) phosphonate, neodymium (2-ethylhexyl)phosphonate,neodymium decyl phosphonate, neodymium dodecyl phosphonate, neodymiumoctadecyl phosphonate, neodymium oleyl phosphonate, neodymium phenylphosphonate, neodymium (p-nonylphenyl)phosphonate, neodymium butylbutylphosphonate, neodymium pentyl pentylphosphonate, neodymium hexylhexylphosphonate, neodymium heptyl heptylphosphonate, neodymium octyloctylphosphonate, neodymium (1-methylheptyl)(1-methylheptyl)phosphonate, neodymium (2-ethylhexyl)(2-ethylhexyl)phosphonate, neodymium decyl decylphosphonate, neodymiumdodecyl dodecylphosphonate, neodymium octadecyl octadecylphosphonate,neodymium oleyl oleylphosphonate, neodymium phenyl phenylphosphonate,neodymium (p-nonylphenyl) (p-nonylphenyl)phosphonate, neodymium butyl(2-ethylhexyl)phosphonate, neodymium (2-ethylhexyl)butylphosphonate,neodymium (1-methylheptyl) (2-ethylhexyl)phosphonate, neodymium(2-ethylhexyl) (1-methylheptyl)phosphonate, neodymium (2-ethylhexyl)(p-nonylphenyl)phosphonate, and neodymium (p-nonylphenyl(2-ethylhexyl)phosphonate.

Neodymium organophosphinates include neodymium butylphosphinate,neodymium pentylphosphinate, neodymium hexylphosphinate, neodymiumheptylphosphinate, neodymium octylphosphinate, neodymium(1-methylheptyl)phosphinate, neodymium (2-ethylhexyl)phosphinate,neodymium decylphosphinate, neodymium dodecylphosphinate, neodymiumoctadecylphosphinate, neodymium oleylphosphinate, neodymiumphenylphosphinate, neodymium (p-nonylphenyl)phosphinate, neodymiumdibutylphosphinate, neodymium dipentylphosphinate, neodymiumdihexylphosphinate, neodymium diheptylphosphinate, neodymiumdioctylphosphinate, neodymium bis(1-methylheptyl)phosphinate, neodymiumbis(2-ethylhexyl)phosphinate, neodymium didecylphosphinate, neodymiumdidodecylphosphinate, neodymium dioctadecylphosphinate, neodymiumdioleylphosphinate, neodymium diphenylphosphinate, neodymiumbis(p-nonylphenyl)phosphinate, neodymium butyl(2-ethylhexyl)phosphinate, neodymium (1-methylheptyl)(2-ethylhexyl)phosphinate, and neodymium(2-ethylhexyl)(p-nonylphenyl)phosphinate.

Neodymium carbamates include neodymium dimethylcarbamate, neodymiumdiethylcarbamate, neodymium diisopropylcarbamate, neodymiumdibutylcarbamate, and neodymium dibenzylcarbamate.

Neodymium dithiocarbamates include neodymium dimethyldithiocarbamate,neodymium diethyldithiocarbamate, neodymium diisopropyldithiocarbamate,neodymium dibutyldithiocarbamate, and neodymium dibenzyldithiocarbamate.

Neodymium xanthates include neodymium methylxanthate, neodymiumethylxanthate, neodymium isopropylxanthate, neodymium butylxanthate, andneodymium benzylxanthate.

Neodymium β-diketonates include neodymium acetylacetonate, neodymiumtrifluoroacetylacetonate, neodymium hexafluoroacetylacetonate, neodymiumbenzoylacetonate, and neodymium 2,2,6,6-tetramethyl-3,5-heptanedionate.

Neodymium alkoxides or aryloxides include neodymium methoxide, neodymiumethoxide, neodymium isopropoxide, neodymium 2-ethylhexoxide, neodymiumphenoxide, neodymium nonylphenoxide, and neodymium naphthoxide.

Suitable neodymium pseudo-halides include neodymium cyanide, neodymiumcyanate, neodymium thiocyanate, neodymium azide, and neodymiumferrocyanide.

The term organolanthanide compound may refer to any lanthanide compoundcontaining at least one lanthanide-carbon bond. These compounds arepredominantly, though not exclusively, those containing cyclopentadienyl(Cp), substituted cyclopentadienyl, allyl, and substituted allylligands. Suitable organolanthanide compounds include Cp₃Ln, Cp₂LnR,Cp₂LnCl, CpLnCl₂, CpLn(cyclooctatetraene), (C₅Me₅)₂LnR, LnR₃,Ln(allyl)₃, and Ln(allyl)₂Cl, where Ln represents a lanthanide atom, andR represents a hydrocarbyl group.

Aluminoxanes include oligomeric linear aluminoxanes that can berepresented by the general formula:

and oligomeric cyclic aluminoxanes that can be represented by thegeneral formula:

where x may be an integer of 1 to about 100, and in other embodimentsabout 10 to about 50; y may be an integer of 2 to about 100, and inother embodiments about 3 to about 20; and where each R¹, which may bethe same or different, may be a mono-valent organic group that isattached to the aluminum atom via a carbon atom. In one or moreembodiments, each R¹ is a hydrocarbyl group such as, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, substituted aryl, aralkyl, alkaryl,allyl, and alkynyl groups. These hydrocarbyl groups may containheteroatoms such as, but not limited to, nitrogen, oxygen, boron,silicon, sulfur, and phosphorus atoms. In one or more embodiments, thealuminoxanes may be soluble in a hydrocarbon solvent. It should be notedthat the number of moles of the aluminoxane as used in this applicationrefers to the number of moles of the aluminum atoms rather than thenumber of moles of the oligomeric aluminoxane molecules. This conventionis commonly employed in the art of catalysis utilizing aluminoxanes.

Aluminoxanes can be prepared by reacting trihydrocarbylaluminumcompounds with water. This reaction can be performed according to knownmethods, such as (1) a method in which the trihydrocarbylaluminumcompound may be dissolved in an organic solvent and then contacted withwater, (2) a method in which the trihydrocarbylaluminum compound may bereacted with water of crystallization contained in, for example, metalsalts, or water adsorbed in inorganic or organic compounds, and (3) amethod in which the trihydrocarbylaluminum compound may be reacted withwater in the presence of the monomer or monomer solution that is to bepolymerized.

Aluminoxane compounds include methylaluminoxane (MAO), modifiedmethylaluminoxane (MMAO), ethylaluminoxane, n-propylaluminoxane,isopropylaluminoxane, butylaluminoxane, isobutylaluminoxane,n-pentylaluminoxane, neopentylaluminoxane, n-hexylaluminoxane,n-octylaluminoxane, 2-ethylhexylaluminoxane, cyclohexylaluminoxane,1-methylcyclopentylaluminoxane, phenylaluminoxane,2,6-dimethylphenylaluminoxane, and the like, and mixtures thereof.Modified methylaluminoxane can be formed by substituting about 20-80% ofthe methyl groups of methylaluminoxane with C₂ to C₁₂ hydrocarbylgroups, preferably with isobutyl groups, by using techniques known tothose skilled in the art.

Various organoaluminum compounds or mixtures thereof can be used as theorganoaluminum compound other than an aluminoxane. The term“organoaluminum compounds” refers to any aluminum compound containing atleast one aluminum-carbon bond. In one or more embodiments,organoaluminum compounds other than aluminoxanes include thoserepresented by the formula AlR_(n)X_(3-n), where each R, which may bethe same or different, is a mono-valent organic group that is attachedto the aluminum atom via a carbon atom, where each X, which may be thesame or different, is a hydrogen atom, a carboxylate group, an alkoxidegroup, or an aryloxide group, and where n is an integer of 1 to 3. Inone or more embodiments, each R may be a hydrocarbyl group such as, butnot limited to, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,cycloalkenyl, substituted cycloalkenyl, aryl, substituted aryl, aralkyl,alkaryl, allyl, and alkynyl groups. These hydrocarbyl groups may containheteroatoms such as, but not limited to, nitrogen, oxygen, boron,silicon, sulfur, and phosphorus atoms.

Organoaluminum compounds other than an aluminoxane include, but are notlimited to, trihydrocarbylaluminum, dihydrocarbylaluminum hydride,hydrocarbylaluminum dihydride, dihydrocarbylaluminum carboxylate,hydrocarbylaluminum bis(carboxylate), dihydrocarbylaluminum alkoxide,hydrocarbylaluminum dialkoxide, dihydrocarbylaluminum aryloxide, andhydrocarbylaluminum diaryloxide compounds.

Trihydrocarbylaluminum compounds include trimethylaluminum,triethylaluminum, triisobutylaluminum, tri-n-propylaluminum,triisopropylaluminum, tri-n-butylaluminum, tri-t-butylaluminum,tri-n-pentylaluminum, trineopentylaluminum, tri-n-hexylaluminum,tri-n-octylaluminum, tris(2-ethylhexyl)aluminum, tricyclohexylaluminum,tris(1-methylcyclopentyl)aluminum, triphenylaluminum,tri-p-tolylaluminum, tris(2,6-dimethylphenyl)aluminum,tribenzylaluminum, diethylphenylaluminum, diethyl-p-tolylaluminum,diethylbenzylaluminum, ethyldiphenylaluminum, ethyldi-p-tolylaluminum,and ethyldibenzylaluminum.

Dihydrocarbylaluminum hydride compounds include diethylaluminum hydride,di-n-propylaluminum hydride, diisopropylaluminum hydride,di-n-butylaluminum hydride, diisobutylaluminum hydride,di-n-octylaluminum hydride, diphenylaluminum hydride, di-p-tolylaluminumhydride, dibenzylaluminum hydride, phenylethylaluminum hydride,phenyl-n-propylaluminum hydride, phenylisopropylaluminum hydride,phenyl-n-butylaluminum hydride, phenylisobutylaluminum hydride,phenyl-n-octylaluminum hydride, p-tolylethylaluminum hydride,p-tolyl-n-propylaluminum hydride, p-tolylisopropylaluminum hydride,p-tolyl-n-butylaluminum hydride, p-tolylisobutylaluminum hydride,p-tolyl-n-octylaluminum hydride, benzylethylaluminum hydride,benzyl-n-propylaluminum hydride, benzylisopropylaluminum hydride,benzyl-n-butylaluminum hydride, benzylisobutylaluminum hydride, andbenzyl-n-octylaluminum hydride.

Hydrocarbylaluminum dihydrides include ethylaluminum dihydride,n-propylaluminum dihydride, isopropylaluminum dihydride, n-butylaluminumdihydride, isobutylaluminum dihydride, and n-octylaluminum dihydride.

Other organoaluminum compounds other than an aluminoxane include, butare not limited to, dimethylaluminum hexanoate, diethylaluminum octoate,diisobutylaluminum 2-ethylhexanoate, dimethylaluminum neodecanoate,diethylaluminum stearate, diisobutylaluminum oleate, methylaluminumbis(hexanoate), ethylaluminum bis(octoate), isobutylaluminumbis(2-ethylhexanoate), methylaluminum bis(neodecanoate), ethylaluminumbis(stearate), isobutylaluminum bis(oleate), dimethylaluminum methoxide,diethylaluminum methoxide, diisobutylaluminum methoxide,dimethylaluminum ethoxide, diethylaluminum ethoxide, diisobutylaluminumethoxide, dimethylaluminum phenoxide, diethylaluminum phenoxide,diisobutylaluminum phenoxide, methylaluminum dimethoxide, ethylaluminumdimethoxide, isobutylaluminum dimethoxide, methylaluminum diethoxide,ethylaluminum diethoxide, isobutylaluminum diethoxide, methylaluminumdiphenoxide, ethylaluminum diphenoxide, isobutylaluminum diphenoxide,and the like, and mixtures thereof.

Useful bromine-containing compounds include elemental bromine,bromine-containing mixed halogens, and organic bromides. In one or moreembodiments, the bromine-containing compounds may be soluble in ahydrocarbon solvent. In other embodiments, hydrocarbon-insolublebromine-containing compounds, which can be suspended in thepolymerization medium to form the catalytically active species, may beuseful.

Bromine-containing mixed halogens include at least one bromine atombonded to at least one other halogen atom besides bromine. Suitablebromine-containing mixed halogens include bromine monofluoride, brominetrifluoride, bromine pentafluoride, bromine monochloride, and iodinemonobromide.

Organic bromides include those compounds that include at least onebromine-carbon bond. In one or more embodiments, the organic bromidesmay be defined by the formula R_(4-x)CBr_(x), where x is an integer from1 to 4, and each R is independently a monovalent organic group, ahydrogen atom, or a halogen atom. In particular embodiments, each R isindependently a hydrogen atom or a hydrocarbyl group. Hydrocarbyl groupsinclude, but are not limited to, alkyl, cycloalkyl, substitutedcycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl,substituted aryl, aralkyl, alkaryl, allyl, and alkynyl groups. Thesehydrocarbyl groups may contain heteroatoms such as, but not limited to,nitrogen, oxygen, boron, silicon, sulfur, and phosphorus atoms.

Types of organic bromides include, but are not limited to, brominatedhydrocarbons, acyl bromides, and brominated carboxylic esters.

Examples of brominated hydrocarbons include, but are not limited to,carbon tetrabromide, tribromomethane (also called bromoform),bromomethane, dibromomethane, t-butyl bromide, 1-bromopropane,2-bromopropane, 1,3-dibromopropane, 2,2-dimethyl-1-bromopropane (alsocalled neopentyl bromide), allyl bromide, benzyl bromide, diphenylmethylbromide, triphenylmethyl bromide, bromobenzene, and benzylidene bromide(also called α,α-dibromotoluene or benzal bromide).

Examples of acyl bromides include, but are not limited to, formylbromide, acetyl bromide, propionyl bromide, butyryl bromide, isobutyrylbromide, valeroyl bromide, isovaleryl bromide, hexanoyl bromide, andbenzoyl bromide.

Examples of brominated carboxylic esters include, but are not limitedto, methyl bromoformate, methyl bromoacetate, methyl 2-bromopropionate,methyl 3-bromopropionate, methyl 2-bromobutyrate, methyl2-bromohexanoate, methyl 4-bromocrotonate, methyl 2-bromobenzoate,methyl 3-bromobenzoate, and methyl 4-bromobenzoate.

Iodine-containing compounds may include elemental iodine,iodine-containing mixed halogens, hydrogen iodide, organic iodides,inorganic iodides, metallic iodides, and organometallic iodides.

Suitable iodine-containing mixed halogens include iodine monochloride,iodine monobromide, iodine trichloride, iodine pentafluoride, iodinemonofluoride, and iodine triflouride.

Suitable organic iodides include iodomethane, diiodomethane,triiodomethane (also called iodoform), tetraiodomethane, 1-iodopropane,2-iodopropane, 1,3-diiodopropane, t-butyl iodide,2,2-dimethyl-1-iodopropane (also called neopentyl iodide), allyl iodide,iodobenzene, benzyl iodide, diphenylmethyl iodide, triphenylmethyliodide, benzylidene iodide (also called benzal iodide orα,α-diiodotoluene), trimethylsilyl iodide, triethylsilyl iodide,triphenylsilyl iodide, dimethyldiiodosilane, diethyldiiodosilane,diphenyldiiodosilane, methyltriiodosilane, ethyltriiodosilane,phenyltriiodosilane, benzoyl iodide, propionyl iodide, and methyliodoformate.

Suitable inorganic iodides include silicon tetraiodide, arsenictriiodide, tellurium tetraiodide, boron triiodide, phosphorus triiodide,phosphorus oxyiodide, and selenium tetraiodide.

Suitable metallic iodides include aluminum triiodide, gallium triiodide,indium triiodide, titanium tetraiodide, zinc diiodide, germaniumtetraiodide, tin tetraiodide, tin diiodide, antimony triiodide, andmagnesium diiodide.

Suitable organometallic iodides include methylmagnesium iodide,dimethylaluminum iodide, diethylaluminum iodide, di-n-butylaluminumiodide, diisobutylaluminum iodide, di-n-octylaluminum iodide,methylaluminum diiodide, ethylaluminum diiodide, n-butylaluminumdiiodide, isobutylaluminum diiodide, methylaluminum sesquiiodide,ethylaluminum sesquiiodide, isobutylaluminum sesquiiodide,ethylmagnesium iodide, n-butylmagnesium iodide, isobutylmagnesiumiodide, phenylmagnesium iodide, benzylmagnesium iodide, trimethyltiniodide, triethyltin iodide, tri-n-butyltin iodide, di-n-butyltindiiodide, and di-t-butyltin diiodide.

In one or more embodiments, dihydrocarbyl ethers include those compoundsrepresented by the formula R—O—R, where each R, which may be the same ordifferent, is a hydrocarbyl group or substituted hydrocarbyl group. Thehydrocarbyl group may contain heteroatoms such as, but not limited to,nitrogen, oxygen, silicon, tin, sulfur, boron, and phosphorous atoms.Examples of hydrocarbyl groups or substituted hydrocarbyl groupsinclude, but are not limited to, alkyl, cycloalkyl, substitutedcycloalkyl, alkenyl, cycloalkenyl, aryl, substituted aryl groups andheterocyclic groups.

Exemplary alkyl groups include methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, t-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl,n-heptyl, 2-ethylhexyl, n-octyl, n-nonyl, and n-decyl groups.

Exemplary cycloalkyl groups include cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, 2-methylcyclohexyl, 2-t-butylcyclohexyl and4-t-butylcyclohexyl groups.

Exemplary aryl groups include phenyl, substituted phenyl, biphenyl,substituted biphenyl, bicyclic aryl, substituted bicyclic aryl,polycyclic aryl, and substituted polycyclic aryl groups. Substitutedaryl groups include those where a hydrogen atom is replaced by amono-valent organic group such as a hydrocarbyl group.

Exemplary substituted phenyl groups include 2-methylphenyl,3-methylphenyl, 4-methylphenyl, 2,3-dimethylphenyl, 3,4-dimethylphenyl,2,5-dimethylphenyl, 2,6-dimethylphenyl, and 2,4,6-trimethylphenyl (alsocalled mesityl) groups.

Exemplary bicyclic or polycyclic aryl groups include 1-naphthyl,2-napthyl, 9-anthryl, 9-phenanthryl, 2-benzo[b]thienyl,3-benzo[b]thienyl, 2-naphtho[2,3-b]thienyl, 2-thianthrenyl,1-isobenzofuranyl, 2-xanthenyl, 2-phenoxathiinyl, 2-indolizinyl,N-methyl-2-indolyl, N-methyl-indazol-3-yl, N-methyl-8-purinyl,3-isoquinolyl, 2-quinolyl, 3-cinnolinyl, 2-pteridinyl,N-methyl-2-carbazolyl, N-methyl-β-carbolin-3-yl, 3-phenanthridinyl,2-acridinyl, 1-phthalazinyl, 1,8-naphthyridin-2-yl, 2-quinoxalinyl,2-quinazolinyl, 1,7-phenanthrolin-3-yl, 1-phenazinyl,N-methyl-2-phenothiazinyl, 2-phenarsazinyl, and N-methyl-2-phenoxazinylgroups.

Exemplary heterocyclic groups include 2-thienyl, 3-thienyl, 2-furyl,3-furyl, N-methyl-2-pyrrolyl, N-methyl-3-pyrrolyl,N-methyl-2-imidazolyl, 1-pyrazolyl, N-methyl-3-pyrazolyl,N-methyl-4-pyrazolyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, pyrazinyl,2-pyrimidinyl, 3-pyridazinyl, 3-isothiazolyl, 3-isoxazolyl, 3-furazanyl,2-triazinyl, morpholinyl, thiomorpholinyl, piperidinyl, piperazinyl,pyrrolidinyl, pyrrolinyl, imidazolidinyl, and imidazolinyl groups.

Suitable types of dihydrocarbyl ethers include, but are not limited to,dialkyl ethers, dicycloalkyl ethers, diaryl ethers, and mixeddihydrocarbyl ethers.

Specific examples of dialkyl ethers include dimethyl ether, diethylether, di-n-propyl ether, diisopropyl ether, di-n-butyl ether,diisobutyl ether, di-t-butyl ether, di-n-pentyl ether, diisopentylether, dineopentyl ether, di-n-hexyl ether, di-n-heptyl ether,di-2-ethylhexyl ether, di-n-octyl ether, di-n-nonyl ether, di-n-decylether, and dibenzyl ether.

Specific examples of dicycloalkyl ethers include dicyclopropyl ether,dicyclobutyl ether, dicyclopentyl ether, dicyclohexyl ether,di-2-methylcyclohexyl ether, and di-2-t-butylcyclohexyl ether.

Specific examples of diaryl ethers include diphenyl ether, di-o-tolylether, di-m-tolyl ether, and di-p-tolyl ether.

Specific examples of mixed dihydrocarbyl ethers include n-butyl methylether, isobutyl methyl ether, sec-butyl methyl ether, t-butyl methylether, n-butyl ethyl ether, isobutyl ethyl ether, sec-butyl ethyl ether,t-butyl ethyl ether, t-amyl methyl ether, t-amyl ethyl ether, phenylethyl ether, phenyl n-propyl ether, phenyl isopropyl ether, phenyln-butyl ether, phenyl isobutyl ether, phenyl n-octyl ether, p-tolylethyl ether, p-tolyl n-propyl ether, p-tolyl isopropyl ether, p-tolyln-butyl ether, p-tolyl isobutyl ether, p-tolyl t-butyl ether, p-tolyln-octyl ether, benzyl n-ethyl ether, benzyl n-propyl ether, benzylisopropyl ether, benzyl n-butyl ether, benzyl isobutyl ether, benzylt-butyl ether, and benzyl n-octyl ether.

In one or more embodiments, one or both of the hydrocarbyl groups (R) inthe dihydrocarbyl ether may contain one or more additional etherlinkages (i.e., C—O—C). These ether compounds may be referred to aspolyethers. Specific examples of polyethers include glyme ethers such asethylene glycol dimethyl ether (also called monoglyme), ethylene glycoldiethyl ether, diethylene glycol dimethyl ether (also called diglyme),diethylene glycol diethyl ether, diethylene glycol di-n-butyl ether,triethylene glycol dimethyl ether (also called triglyme), triethyleneglycol diethyl ether, tetraethylene glycol dimethyl ether (also calledtetraglyme), and tetraethylene glycol diethyl ether.

The catalyst composition of this invention may be formed by combining ormixing the foregoing catalyst ingredients. Although one or more activecatalyst species are believed to result from the combination of thecatalyst ingredients, the degree of interaction or reaction between thevarious catalyst ingredients or components is not known with any greatdegree of certainty. The combination or reaction product of thelanthanide compound, the aluminoxane, the organoaluminum compound otherthan an aluminoxane, and the bromine-containing compound isconventionally referred to as a catalyst system or catalyst composition.The dihydrocarbyl ether, as used herein, may be referred to as acomponent of that system or as a modifier to that system. In thisrespect, reference to catalyst ingredients refers to the lanthanidecompound, the aluminoxane, the organoaluminum compound other than analuminoxane, the bromine-containing compound, and the dihydrocarbylether. The term modified catalyst composition or modified catalystsystem may be employed to encompass a simple mixture of the ingredients,a complex of the various ingredients that is caused by physical orchemical forces of attraction, a chemical reaction product of theingredients, or a combination of the foregoing.

The catalyst composition of this invention advantageously has atechnologically useful catalytic activity for polymerizing conjugateddienes into polydienes over a wide range of catalyst concentrations andcatalyst ingredient ratios. Several factors may impact the optimumconcentration of any one of the catalyst ingredients. For example,because the catalyst ingredients may interact to form an active species,the optimum concentration for any one catalyst ingredient may bedependent upon the concentrations of the other catalyst ingredients.

In one or more embodiments, the molar ratio of the aluminoxane to thelanthanide compound (aluminoxane/Ln) can be varied from 5:1 to about1,000:1, in other embodiments from about 10:1 to about 700:1, and inother embodiments from about 20:1 to about 500:1.

In one or more embodiments, the molar ratio of the organoaluminumcompound other than an aluminoxane to the lanthanide compound (Al/Ln)can be varied from about 1:1 to about 200:1, in other embodiments fromabout 2:1 to about 150:1, and in other embodiments from about 5:1 toabout 100:1.

The molar ratio of the bromine-containing compound to the lanthanidecompound is best described in terms of the ratio of the moles of bromineatoms in the bromine-containing compound to the moles of lanthanideatoms in the lanthanide compound (Br/Ln). In one or more embodiments,the bromine/Ln molar ratio can be varied from about 0.5:1 to about 20:1,in other embodiments from about 1:1 to about 10:1, and in otherembodiments from about 2:1 to about 6:1.

In these or other embodiments, the molar ratio of the iodine atoms inthe iodine-containing compounds to the bromine atoms in thebromine-containing compounds (I/Br) may be varied from about 0.1:1 toabout 10:1, in other embodiments from about 0.5:1 to about 5:1, and inother embodiments from about 0.8:1 to about 2:1.

In one or more embodiments, the molar ratio of the dihydrocarbyl etherto the lanthanide compound (ether/Ln) can be varied from 0.5:1 to about1,000:1, in other embodiments from about 1:1 to about 700:1, and inother embodiments from about 5:1 to about 500:1.

The lanthanide-based catalyst can be formed by employing severaltechniques. For example, the catalyst may be formed by adding thecatalyst components directly to the monomer to be polymerized. In thisrespect, the catalyst components including the dihydrocarbyl ether maybe added either in a stepwise or simultaneous manner. In one embodiment,when the catalyst ingredients are added in a stepwise manner, thedihydrocarbyl ether can be added first, followed by the aluminoxane,followed by the lanthanide compound, followed by the organoaluminumcompound other than aluminoxane, and ultimately followed by thebromine-containing compound optionally with the iodine-containingcompound. Where both a bromine-containing compound and aniodine-containing compound are employed, they may be pre-mixed with oneanother or added individually. The addition of the catalyst componentsdirectly and individually to the monomer to be polymerized may bereferred to as an in situ formation of the catalyst system.

In other embodiments, the catalyst may be preformed. That is, thecatalyst ingredients including the dihydrocarbyl ether may be introducedand pre-mixed outside of the monomer to be polymerized. In particularembodiments, the preformation of the catalyst may occur either in theabsence of any monomer or in the presence of a small amount of at leastone conjugated diene monomer at an appropriate temperature, which isgenerally from about −20° C. to about 80° C. Mixtures of conjugateddiene monomers may also be used. The amount of conjugated diene monomerthat may be used for preforming the catalyst can range from about 1 toabout 500 moles, in other embodiments from about 5 to about 250 moles,and in other embodiments from about 10 to about 100 moles per mole ofthe lanthanide compound. The resulting preformed catalyst compositioncan be aged, if desired, prior to being added to the monomer that is tobe polymerized.

In other embodiments, the catalyst may be formed by using a two-stageprocedure. The first stage can involve combining the lanthanide compoundwith the aluminoxane and the organoaluminum compound other than analuminoxane either in the absence of any monomer or in the presence of asmall amount of at least one conjugated diene monomer at an appropriatetemperature (e.g., −20° C. to about 80° C.). The amount of monomeremployed in preparing this first-stage mixture may be similar to thatset forth above for preforming the catalyst. In the second stage, themixture prepared in the first stage, the dihydrocarbyl ether, and thebromine-containing compound optionally together with theiodine-containing compound can be added in either a stepwise orsimultaneous manner to the monomer that is to be polymerized. In oneembodiment, the dihydrocarbyl ether can be added first, followed by themixture prepared in the first stage, and then followed by thebromine-containing compound optionally together with theiodine-containing compound.

In one or more embodiments, a solvent may be employed as a carrier toeither dissolve or suspend the catalyst or catalyst ingredients in orderto facilitate the delivery of the catalyst or catalyst ingredients tothe polymerization system. In other embodiments, conjugated dienemonomer can be used as the catalyst carrier. In yet other embodiments,the catalyst ingredients can be used in their neat state without anysolvent.

In one or more embodiments, suitable solvents include those organiccompounds that will not undergo polymerization or incorporation intopropagating polymer chains during the polymerization of monomer in thepresence of catalyst. In one or more embodiments, these organic speciesare liquid at ambient temperature and pressure. In one or moreembodiments, these organic solvents are inert to the catalyst. Exemplaryorganic solvents include hydrocarbons with a low or relatively lowboiling point such as aromatic hydrocarbons, aliphatic hydrocarbons, andcycloaliphatic hydrocarbons. Non-limiting examples of aromatichydrocarbons include benzene, toluene, xylenes, ethylbenzene,diethylbenzene, and mesitylene. Non-limiting examples of aliphatichydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, n-nonane,n-decane, isopentane, isohexanes, isopentanes, isooctanes,2,2-dimethylbutane, petroleum ether, kerosene, and petroleum spirits.And, non-limiting examples of cycloaliphatic hydrocarbons includecyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane.Mixtures of the above hydrocarbons may also be used. As is known in theart, aliphatic and cycloaliphatic hydrocarbons may be desirably employedfor environmental reasons. The low-boiling hydrocarbon solvents aretypically separated from the polymer upon completion of thepolymerization.

Other examples of organic solvents include high-boiling hydrocarbons ofhigh molecular weights, such as paraffinic oil, aromatic oil, or otherhydrocarbon oils that are commonly used to oil-extend polymers. Sincethese hydrocarbons are non-volatile, they typically do not requireseparation and remain incorporated in the polymer.

The production of polydienes according to this invention can beaccomplished by polymerizing conjugated diene monomer in the presence ofa catalytically effective amount of the foregoing catalyst composition.The introduction of the catalyst composition, the conjugated dienemonomer, and any solvent if employed forms a polymerization mixture inwhich the polymer product is formed. The total catalyst concentration tobe employed in the polymerization mixture may depend on the interplay ofvarious factors such as the purity of the ingredients, thepolymerization temperature, the polymerization rate and conversiondesired, the molecular weight desired, and many other factors.Accordingly, a specific total catalyst concentration cannot bedefinitively set forth except to say that catalytically effectiveamounts of the respective catalyst ingredients can be used. In one ormore embodiments, the amount of the lanthanide compound used can bevaried from about 0.01 to about 2 mmol, in other embodiments from about0.02 to about 1 mmol, and in other embodiments from about 0.05 to about0.5 mmol per 100 g of conjugated diene monomer.

In one or more embodiments, the polymerization system employed may begenerally considered a bulk polymerization system that includessubstantially no solvent or a minimal amount of solvent. Those skilledin the art will appreciate the benefits of bulk polymerization processes(i.e., processes where monomer acts as the solvent), and therefore thepolymerization system includes less solvent than will deleteriouslyimpact the benefits sought by conducting bulk polymerization. In one ormore embodiments, the solvent content of the polymerization mixture maybe less than about 20% by weight, in other embodiments less than about10% by weight, and in still other embodiments less than about 5% byweight based on the total weight of the polymerization mixture. In stillanother embodiment, the polymerization mixture is substantially devoidof solvent, which refers to the absence of that amount of solvent thatwould otherwise have an appreciable impact on the polymerizationprocess. Polymerization systems that are substantially devoid of solventmay be referred to as including substantially no solvent. In particularembodiments, the polymerization mixture is devoid of solvent.

The polymerization may be conducted in any conventional polymerizationvessels known in the art. In one or more embodiments, solutionpolymerization can be conducted in a conventional stirred-tank reactor.In other embodiments, bulk polymerization can be conducted in aconventional stirred-tank reactor, especially if the monomer conversionis less than about 60%. In still other embodiments, especially where themonomer conversion in a bulk polymerization process is higher than about60%, which typically results in a highly viscous cement, the bulkpolymerization may be conducted in an elongated reactor in which theviscous cement under polymerization is driven to move by piston, orsubstantially by piston. For example, extruders in which the cement ispushed along by a self-cleaning single-screw or double-screw agitatorare suitable for this purpose. Examples of useful bulk polymerizationprocesses are disclosed in U.S. Publication No. 2005/0197474 A1, whichis incorporated herein by reference.

In one or more embodiments, all of the ingredients used for thepolymerization can be combined within a single vessel (e.g., aconventional stirred-tank reactor), and all steps of the polymerizationprocess can be conducted within this vessel. In other embodiments, twoor more of the ingredients can be pre-combined in one vessel and thentransferred to another vessel where the polymerization of monomer (or atleast a major portion thereof) may be conducted.

The polymerization can be carried out as a batch process, a continuousprocess, or a semi-continuous process. In the semi-continuous process,the monomer is intermittently charged as needed to replace that monomeralready polymerized. In one or more embodiments, the conditions underwhich the polymerization proceeds may be controlled to maintain thetemperature of the polymerization mixture within a range from about −10°C. to about 200° C., in other embodiments from about 0° C. to about 150°C., and in other embodiments from about 20° C. to about 100° C. In oneor more embodiments, the heat of polymerization may be removed byexternal cooling by a thermally controlled reactor jacket, internalcooling by evaporation and condensation of the monomer through the useof a reflux condenser connected to the reactor, or a combination of thetwo methods. Also, conditions may be controlled to conduct thepolymerization under a pressure of from about 0.1 atmosphere to about 50atmospheres, in other embodiments from about 0.5 atmosphere to about 20atmospheres, and in other embodiments from about 1 atmosphere to about10 atmospheres. In one or more embodiments, the pressures at which thepolymerization may be carried out include those that ensure that themajority of the monomer is in the liquid phase. In these or otherembodiments, the polymerization mixture may be maintained underanaerobic conditions.

The polydienes produced by the polymerization process of this inventionmay possess pseudo-living characteristics, such that some of polymerchains in these polymers have reactive chain ends. Once a desiredmonomer conversion is achieved, a functionalizing agent may optionallybe introduced into the polymerization mixture to react with any reactivepolymer chains so as to give a functionalized polymer. In one or moreembodiments, the functionalizing agent is introduced prior to contactingthe polymerization mixture with a quenching agent. In other embodiments,the functionalizing agent may be introduced after the polymerizationmixture has been partially quenched with a quenching agent.

In one or more embodiments, functionalizing agents include compounds orreagents that can react with a reactive polymer produced by thisinvention and thereby provide the polymer with a functional group thatis distinct from a propagating chain that has not been reacted with thefunctionalizing agent. The functional group may be reactive orinteractive with other polymer chains (propagating and/ornon-propagating) or with other constituents such as reinforcing fillers(e.g. carbon black) that may be combined with the polymer. In one ormore embodiments, the reaction between the functionalizing agent and thereactive polymer proceeds via an addition or substitution reaction.

Useful functionalizing agents may include compounds that simply providea functional group at the end of a polymer chain without joining two ormore polymer chains together, as well as compounds that can couple orjoin two or more polymer chains together via a functional linkage toform a single macromolecule. The latter type of functionalizing agentsmay also be referred to as coupling agents.

In one or more embodiments, functionalizing agents include compoundsthat will add or impart a heteroatom to the polymer chain. In particularembodiments, functionalizing agents include those compounds that willimpart a functional group to the polymer chain to form a functionalizedpolymer that reduces the 50° C. hysteresis loss of a carbon-black filledvulcanizates prepared from the functionalized polymer as compared tosimilar carbon-black filled vulcanizates prepared fromnon-functionalized polymer. In one or more embodiments, this reductionin hysteresis loss is at least 5%, in other embodiments at least 10%,and in other embodiments at least 15%.

In one or more embodiments, suitable functionalizing agents includethose compounds that contain groups that may react with pseudo-livingpolymers (e.g., those produced in accordance with this invention).Exemplary functionalizing agents include ketones, quinones, aldehydes,amides, esters, isocyanates, isothiocyanates, epoxides, imines,aminoketones, aminothioketones, and acid anhydrides. Examples of thesecompounds are disclosed in U.S. Pat. Nos. 4,906,706, 4,990,573,5,064,910, 5,567,784, 5,844,050, 6,838,526, 6,977,281, and 6,992,147;U.S. Pat. Publication Nos. 2006/0004131 A1, 2006/0025539 A1,2006/0030677 A1, and 2004/0147694 A1; Japanese Patent Application Nos.05-051406A, 05-059103A, 10-306113A, and 11-035633A; which areincorporated herein by reference. Other examples of functionalizingagents include azine compounds as described in U.S. Ser. No. 11/640,711,hydrobenzamide compounds as disclosed in U.S. Ser. No. 11/710,713, nitrocompounds as disclosed in U.S. Ser. No. 11/710,845, and protected oximecompounds as disclosed in U.S. Publication No. 2008-0146745 A1, all ofwhich are incorporated herein by reference.

In particular embodiments, the functionalizing agents employed may becoupling agents which include, but are not limited to, metal halidessuch as tin tetrachloride, metalloid halides such as silicontetrachloride, metal ester-carboxylate complexes such as dioctyltinbis(octylmaleate), alkoxysilanes such as tetraethyl orthosilicate, andalkoxystannanes such as tetraethoxytin. Coupling agents can be employedeither alone or in combination with other functionalizing agents. Thecombination of functionalizing agents may be used in any molar ratio.

The amount of functionalizing agent introduced to the polymerizationmixture may depend upon various factors including the type and amount ofcatalyst used to initiate the polymerization, the type offunctionalizing agent, the desired level of functionality and many otherfactors. In one or more embodiments, the amount of functionalizing agentmay be in a range of from about 1 to about 200 moles, in otherembodiments from about 5 to about 150 moles, and in other embodimentsfrom about 10 to about 100 moles per mole of the lanthanide compound.

Because reactive polymer chains may slowly self-terminate at hightemperatures, in one embodiment the functionalizing agent may be addedto the polymerization mixture once a peak polymerization temperature isobserved. In other embodiments, the functionalizing agent may be addedwithin about 25 to 35 minutes after the peak polymerization temperatureis reached.

In one or more embodiments, the functionalizing agent may be introducedto the polymerization mixture after a desired monomer conversion isachieved but before a quenching agent containing a protic hydrogen atomis added. In one or more embodiments, the functionalizing agent is addedto the polymerization mixture after a monomer conversion of at least 5%,in other embodiments at least 10%, in other embodiments at least 20%, inother embodiments at least 50%, and in other embodiments at least 80%.In these or other embodiments, the functionalizing agent is added to thepolymerization mixture prior to a monomer conversion of 90%, in otherembodiments prior to 70% monomer conversion, in other embodiments priorto 50% monomer conversion, in other embodiments prior to 20% monomerconversion, and in other embodiments prior to 15% monomer conversion. Inone or more embodiments, the functionalizing agent is added aftercomplete, or substantially complete monomer conversion. In particularembodiments, a functionalizing agent may be introduced to thepolymerization mixture immediately prior to, together with, or after theintroduction of a Lewis base as disclosed in co-pending U.S. PublicationNo. 2009-0043046 A1, filed on Aug. 7, 2007, which is incorporated hereinby reference.

In one or more embodiments, the functionalizing agent may be introducedto the polymerization mixture at a location (e.g., within a vessel)where the polymerization (or at least a portion thereof) has beenconducted. In other embodiments, the functionalizing agent may beintroduced to the polymerization mixture at a location that is distinctfrom where the polymerization (or at least a portion thereof) has takenplace. For example, the functionalizing agent may be introduced to thepolymerization mixture in downstream vessels including downstreamreactors or tanks, in-line reactors or mixers, extruders, ordevolatilizers.

Once a functionalizing agent has optionally been introduced to thepolymerization mixture and/or a desired reaction time has been provided,a quenching agent can be added to the polymerization mixture in order toinactivate any residual reactive polymer chains and the catalyst orcatalyst components. The quenching agent may be a protic compound, whichincludes, but is not limited to, an alcohol, a carboxylic acid, aninorganic acid, water, or a mixture thereof. In particular embodiments,the quenching agent includes a polyhydroxy compound as disclosed incopending U.S. Ser. No. 11/890,591, filed on Aug. 7, 2007, which isincorporated herein by reference. An antioxidant such as2,6-di-t-butyl-4-methylphenol may be added along with, before, or afterthe addition of the quenching agent. The amount of the antioxidantemployed may be in the range of about 0.2% to about 1% by weight of thepolymer product. The quenching agent and the antioxidant may be added asneat materials or, if necessary, dissolved in a hydrocarbon solvent orconjugated diene monomer prior to being added to the polymerizationmixture.

In one or more embodiments, the quenching agent is added to thepolymerization mixture after a monomer conversion of at least 5%, inother embodiments at least 10%, in other embodiments at least 20%, inother embodiments at least 50%, and in other embodiments at least 80%.In these or other embodiments, the quenching agent is added to thepolymerization mixture prior to a monomer conversion of 90%, in otherembodiments prior to 70% monomer conversion, in other embodiments priorto 50% monomer conversion, in other embodiments prior to 20% monomerconversion, and in other embodiments prior to 15% monomer conversion.

Once the polymerization mixture has been quenched, the variousconstituents of the polymerization mixture may be recovered. In one ormore embodiments, the unreacted monomer can be recovered from thepolymerization mixture. For example, the monomer can be distilled fromthe polymerization mixture by using techniques known in the art. In oneor more embodiments, a devolatilizer may be employed to remove themonomer from the polymerization mixture. Once the monomer has beenremoved from the polymerization mixture, the monomer may be purified,stored, and/or recycled back to the polymerization process.

The polymer product may be recovered from the polymerization mixture byusing techniques known in the art. In one or more embodiments,desolventization and drying techniques may be used. For instance, thepolymer can be recovered by passing the polymerization mixture through aheated screw apparatus, such as a desolventizing extruder, in which thevolatile substances are removed by evaporation at appropriatetemperatures (e.g., about 100° C. to about 170° C.) and underatmospheric or sub-atmospheric pressure. This treatment serves to removeunreacted monomer as well as any low-boiling solvent. Alternatively, thepolymer can also be recovered by subjecting the polymerization mixtureto steam desolventization, followed by drying the resulting polymercrumbs in a hot air tunnel. The polymer can also be recovered bydirectly drying the polymerization mixture on a drum dryer.

Where cis-1,4-polydienes (e.g., cis-1,4-polybutadiene) are produced byone or more embodiments of the process of this invention, thecis-1,4-polydienes may advantageously have a cis-1,4 linkage content inexcess of 96%, in other embodiments in excess of 97%, in otherembodiments in excess of 98%, in other embodiments in excess of 99.0%,in other embodiments in excess of 99.1%, in other embodiments in excessof 99.2%, and in other embodiments in excess of 99.3%. In these or otherembodiments, the polydienes (e.g., cis-1,4-polybutadiene) have amolecular weight distribution of less than 2.5, in other embodimentsless than 2.2, in other embodiments less than 2.0, in other embodimentsless than 1.8, and in other embodiments less than 1.6.

Advantageously, these polymers exhibit excellent viscoelastic propertiesand are particularly useful in the manufacture of various tirecomponents including, but not limited to, tire treads, sidewalls,subtreads, and bead fillers. The cis-1,4-polydienes can be used as allor part of the elastomeric component of a tire stock. When thecis-1,4-polydienes are used in conjunction with other rubbers to formthe elastomeric component of a tire stock, these other rubbers may benatural rubber, synthetic rubbers, and mixtures thereof. Examples ofsynthetic rubber include polyisoprene, poly(styrene-co-butadiene),polybutadiene with low cis-1,4-linkage content,poly(styrene-co-butadiene-co-isoprene), and mixtures thereof. Thecis-1,4-polydienes can also be used in the manufacture of hoses, belts,shoe soles, window seals, other seals, vibration damping rubber, andother industrial products.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES Example 1

The polymerization reactor consisted of a one-gallon stainless cylinderequipped with a mechanical agitator (shaft and blades) capable of mixinghigh viscosity polymer cement. The top of the reactor was connected to areflux condenser system for conveying, condensing, and recycling the1,3-butadiene vapor developed inside the reactor throughout the durationof the polymerization. The reactor was also equipped with a coolingjacket chilled by cold water. The heat of polymerization was dissipatedpartly by internal cooling through the use of the reflux condensersystem, and partly by external cooling through heat transfer to thecooling jacket.

The reactor was thoroughly purged with a stream of dry nitrogen, whichwas then replaced with 1,3-butadiene vapor by charging 100 g of dry1,3-butadiene monomer to the reactor, heating the reactor to 65° C., andthen venting the 1,3-butadiene vapor from the top of the refluxcondenser system until no liquid 1,3-butadiene remained in the reactor.Cooling water was applied to the reflux condenser and the reactorjacket, and 1302 g of 1,3-butadiene monomer and 7.8 mL of dibutyl ether(n-Bu₂O) in hexane was charged into the reactor. After the monomer wasthermostated at 32° C., the polymerization was initiated by charginginto the reactor a preformed catalyst that had been prepared by mixing6.5 g of 19.2 wt % 1,3-butadiene in hexane, 1.44 ml of 0.054 M neodymiumversatate in hexane, 5.20 ml of 1.5 M methylaluminoxane (MAO) intoluene, 2.81 ml of 1.0 M diisobutylaluminum hydride (DIBAH) in hexane,and 3.12 ml of 0.05 M tetrabromomethane (CBr₄) in hexane and allowingthe mixture to age for 15 minutes. After 3.5 minutes from itscommencement, the polymerization was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 143.2 g (11.0% conversion). The Mooneyviscosity (ML₁₊₄) of the polymer was determined to be 21.3 at 100° C. byusing a Monsanto Mooney viscometer with a large rotor, a one-minutewarm-up time, and a four minute running time. As determined by gelpermeation chromatography (GPC), the polymer had a number averagemolecular weight (M_(n)) of 110,000, a weight average molecular weight(M_(w)) of 262,000, and a molecular weight distribution (M_(w)/M_(n)) of2.4. The infrared spectroscopic analysis of the polymer indicated a cis1,4-linkage content of 99.2%, a trans 1,4-linkage content of 0.6%, and a1,2-linkage content of 0.2%.

Example 2 (Comparative Example)

The same procedure as used in Example 1 was used except that 2.50 ml of1.0 M DIBAH in hexane was added, and tetrabromosilane (SiBr₄) was usedinstead of CBr₄. After 20.0 minutes from its commencement, thepolymerization was terminated by diluting the polymerization mixturewith 1360 g of hexane and dropping the batch to 3 gallons of isopropanolcontaining 5 g of 2,6-di-tert-butyl-4-methylphenol. The coagulatedpolymer was drum-dried. The yield of the polymer was 36.9 g (2.8%conversion). The resulting polymer had the following properties:ML₁₊₄=appeared to be very low and was not measured, M_(n)=59,000,M_(w)=164,000, M_(w)/M_(n)=2.8, ds 1,4-linkage content=92.3%, trans1,4-linkage content=5.5%, and 1,2-linkage content=2.2%.

Example 3 (Comparative Example)

The same procedure as used in Example 1 was used except that tin (IV)bromide (SnBr₄) was used instead of CBr₄. After 4.3 minutes from itscommencement, the polymerization formed polymer gel on the agitator ofthe reactor. Upon gel formation, the polymerization was immediatelyterminated by diluting the polymerization mixture with 1360 g of hexaneand dropping the batch to 3 gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 51.4 g (3.9% conversion). The resultingpolymer had the following properties: ML₁₊₄=35.7, M_(n)=85,000,M_(w)=530,000, M_(w)/M_(n)=6.2, cis 1,4-linkage content=99.3%, trans1,4-linkage content=0.5%, and 1,2-linkage content=0.2%.

A comparison of the results (Table 1) obtained in Example 1 with thoseobtained in Comparative Example 2 indicates that the use of CBr₄ insteadof SiBr₄ yields a polymer with a high cis-1,4-linkage content and anarrow molecular weight distribution at a desired Mooney viscosity. Theaddition of SiBr₄ provided a less active catalyst. Comparing Example 1to Comparative Example 3, although SnBr₄ resulted in the formation ofcis-1,4-polybutadiene having a high cis-1,4-linkage content, thecatalyst was too active resulting in the formation of polymer gel duringthe polymerization which led to a broad molecular weight distribution.

TABLE 1 Comparing Polymers Prepared Using Tetrabromo-Compounds. Example1 2 3 Nd/100 g Bd (mmol) 0.006 0.006 0.006 NdV/MAO/DIBAH/halide1/100/36/1 1/100/32/1 1/100/36/1 Bu₂O/Nd 40/1 40/1 40/1 Halide CBr₄SiBr₄ SnBr₄ Gel Formation no no yes Percent Conversion 11.0 2.8 3.9ML₁₊₄ 21.3 very low 35.7 Mn (kg/mol) 110 59 85 Mw (kg/mol) 262 164 530MWD 2.4 2.8 6.2 % cis 99.2 92.3 99.3 % trans 0.6 5.5 0.5 % vinyl 0.2 2.20.2

Example 4

The same procedure as used in Example 1 was used except that2-bromo-2-methylpropane (t-BuBr) was used instead of CBr₄. After 3.0minutes from its commencement, the polymerization was terminated bydiluting the polymerization mixture with 1360 g of hexane and droppingthe batch to 3 gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 134.7 g (10.3% conversion). The resultingpolymer had the following properties: ML₁₊₄=29.9, M_(n)=132,000,M_(w)=269,000, M_(w)/M_(n)=2.0, cis 1,4-linkage content=99.3%, trans1,4-linkage content=0.6%, and 1,2-linkage content=0.1%.

Example 5 (Comparative Example)

The same procedure as used in Example 1 was used except that 2.65 ml of1.0 M DIBAH in hexane was added, and 2-chloro-2-methylpropane (t-BuCl)was used instead of CBr₄. After 2.8 minutes from its commencement, thepolymerization formed polymer gel on the agitator of the reactor. Upongel formation, the polymerization was immediately terminated by dilutingthe polymerization mixture with 1360 g of hexane and dropping the batchto 3 gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 149.0 g (11.4% conversion). The resultingpolymer had the following properties: ML₁₊₄=11.3, M_(n)=111,000,M_(w)=188,000, M_(w)/M_(n)=1.7, cis 1,4-linkage content=98.9%, trans1,4-linkage content=0.9%, and 1,2-linkage content=0.2%.

Example 6 (Comparative Example)

The same procedure as used in Example 1 was used except that 2.50 ml of1.0 M DIBAH in hexane was added, and 2-iodo-2-methylpropane (t-BuI) wasused instead of CBr₄. After 10.0 minutes from its commencement, thepolymerization was terminated by diluting the polymerization mixturewith 1360 g of hexane and dropping the batch to 3 gallons of isopropanolcontaining 5 g of 2,6-di-tert-butyl-4-methylphenol. The coagulatedpolymer was drum-dried. The yield of the polymer was 175.4 g (12.9%conversion). The resulting polymer had the following properties:ML₁₊₄=29.2, M_(n)=156,000, M_(w)=237,000, M_(w)/M_(n)=1.5, cis1,4-linkage content=98.8%, trans 1,4-linkage content=0.9%, and1,2-linkage content=0.3%.

A comparison of the results (Table 2) obtained in Example 4 with thoseobtained in Comparative Example 5 indicates that the use of t-BuBrinstead of t-BuCl yields a polymer with a high cis-1,4-linkage contentand a narrow molecular weight distribution at a desired Mooney viscositywithout the formation of gel during the polymerization. ComparingExample 4 to Comparative Example 6, t-BuBr results in the formation ofcis-1,4-polybutadiene having a higher cis-1,4-linkage content thant-BuI.

TABLE 2 Comparing Polymers Prepared Using Monobromo-Compounds. Example 45 6 Nd/100 g Bd (mmol) 0.006 0.006 0.006 NdV/MAO/DIBAH/halide 1/100/36/21/100/34/2 1/100/32/2 Bu₂O/Nd 40/1 40/1 40/1 Halide t-BuBr t-BuCl t-BuIGel Formation no yes no Percent Conversion 10.3 11.4 12.9 ML₁₊₄ 29.911.3 29.2 Mn (kg/mol) 132 111 156 Mw (kg/mol) 269 188 237 MWD 2.0 1.71.5 % Cis 99.3 98.9 98.8 % Trans 0.6 0.9 0.9 % Vinyl 0.1 0.2 0.3

Example 7

The same procedure as used in Example 1 was used except that 2.73 ml of1.0 M DIBAH in hexane was added. After 2.8 minutes from itscommencement, the polymerization was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 157.2 g (12.1% conversion). The resultingpolymer had the following properties: ML₁₊₄=14.9, M_(n)=117,000,M_(w)=213,000, M_(w)/M_(n)=1.8, cis 1,4-linkage content=99.1%, trans1,4-linkage content=0.7%, and 1,2-linkage content=0.2%.

Example 8 (Comparative Example)

The same procedure as used in Example 1 was used except that theaddition of n-Bu₂O was omitted. After 1.7 minutes from its commencement,the polymerization was immediately terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 164.3 g (12.6% conversion). The resultingpolymer had the following properties: ML₁₊₄=15.2, M_(n)=127,000,M_(w)=179,000, M_(w)/M_(n)=1.4, cis 1,4-linkage content=98.3%, trans1,4-linkage content=1.5%, and 1,2-linkage content=0.2%.

Comparing Example 7 to Comparative Example 8 in Table 3, the addition ofn-Bu₂O increases cis 1,4-linkage content.

Example 9

The same procedure as used in Example 1 was used except that 3.12 ml of0.05 M t-BuBr in hexane was added. After 3.0 minutes from itscommencement, the polymerization was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 134.7 g (10.3% conversion). The resultingpolymer had the following properties: ML₁₊₄=29.9, M_(n)=132,000,M_(w)=269,000, M_(w)/M_(n)=2.0, cis 1,4-linkage content=99.3%, trans1,4-linkage content=0.6%, and 1,2-linkage content=0.1%.

Example 10 (Comparative Example)

The same procedure as used in Example 1 was used except that theaddition of n-Bu₂O was omitted and 3.12 ml of 0.05 M t-BuBr in hexanewas added. After 0.7 minutes from its commencement, the polymerizationformed polymer gel on the agitator of the reactor. Upon gel formation,the polymerization was immediately terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 59.5 g (4.6% conversion). The resultingpolymer had the following properties: ML₁₊₄=8.0, M_(n)=84,000,M_(w)=157,000, M_(w)/M_(n)=1.9, cis 1,4-linkage content=98.5%, trans1,4-linkage content=1.3%, and 1,2-linkage content=0.2%.

Comparing Example 9 to Comparative Example 10 in Table 3, the additionof n-Bu₂O increases cis 1,4-linkage content and prevents formation ofgel during the polymerization reaction.

Example 11

The same procedure as used in Example 1 was used except that 1.56 ml of0.05 M Br₂ in hexane was added. After 3.3 minutes from its commencement,the polymerization was terminated by diluting the polymerization mixturewith 1360 g of hexane and dropping the batch to 3 gallons of isopropanolcontaining 5 g of 2,6-di-tert-butyl-4-methylphenol. The coagulatedpolymer was drum-dried. The yield of the polymer was 160.4 g (12.3%conversion). The resulting polymer had the following properties:ML₁₊₄=23.9, M_(n)=132,000, M_(w)=235,000, M_(w)/M_(n)=1.8, cis1,4-linkage content=99.2%, trans 1,4-linkage content=0.7%, and1,2-linkage content=0.1%.

Example 12 (Comparative Example)

The same procedure as used in Example 1 was used except that theaddition of n-Bu₂O was omitted and 1.56 ml of 0.05 M Br₂ in hexane wasadded. After 0.3 minutes from its commencement, the polymerizationformed polymer gel on the agitator of the reactor. Upon gel formation,the polymerization was immediately terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 67.0 g (5.1% conversion). The resultingpolymer had the following properties: ML₁₊₄=3.7, M_(n)=71,000,M_(w)=127,000, M_(w)/M_(n)=1.8, cis 1,4-linkage content=98.4%, trans1,4-linkage content=1.3%, and 1,2-linkage content=0.3%.

Comparing Example 11 to Comparative Example 12 in Table 3, the additionof n-Bu₂O increases cis 1,4-linkage content and prevents formation ofgel during the polymerization reaction.

TABLE 3 Comparing Bulk Polymerizations Conducted with and withoutn-Bu₂O. Example 7 8 9 10 11 12 Nd/100 g Bd (mmol) 0.006 0.006 0.0060.006 0.006 0.006 NdV/MAO/DIBAH/halide 1/100/35/1 1/100/36/1 1/100/36/21/100/36/2 1/100/44/1 1/100/44/1 Bu₂O/Nd 40/1 0/1 40/1 0/1 40/1 0/1Halide CBr₄ CBr₄ t-BuBr t-BuBr Br₂ Br₂ Gel Formation no no no yes no yesPercent Conversion 12.1 12.6 10.3 4.6 12.3 5.1 ML₁₊₄ 14.9 15.2 29.9 8.023.9 3.7 Mn (kg/mol) 117 127 132 84 132 71 Mw (kg/mol) 213 179 269 157235 127 MWD 1.8 1.4 2.0 1.9 1.8 1.8 % Cis 99.1 98.3 99.3 98.5 99.2 98.4% Trans 0.7 1.5 0.6 1.3 0.7 1.3 % Vinyl 0.2 0.2 0.1 0.2 0.1 0.3

Example 13 (Comparative Example)

The same procedure as used in Example 7 was used except that theaddition of DIBAH was omitted. After 20.0 minutes from its commencement,the polymerization reaction was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. No polymer product was present in themixture. Comparing Example 7 to Comparative Example 13 in Table 4, anorganoaluminum compound (e.g., DIBAH) other than an aluminoxane isnecessary for a polymerization to occur.

Example 14 (Comparative Example)

The same procedure as used in Example 7 was used except that theaddition of MAO was omitted. After 20.0 minutes from its commencement,the polymerization was immediately terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 44.9 g (3.4% conversion). The resultingpolymer had the following properties: ML₁₊₄=26.8, M_(n)=71,000,M_(w)=499,000, M_(w)/M_(n)=7.0, cis 1,4-linkage content=99.0%, trans1,4-linkage content=0.6%, and 1,2-linkage content=0.4%.

Comparing Example 7 in Table 3 to Comparative Example 14 in Table 4, MAOis necessary for a polymerization to occur with a conversion over 10%,cis 1,4-linkage content above 99.0%, and a narrow molecular weightdistribution.

Example 15 (Comparative Example)

The same procedure as used in Example 9 was used except that theaddition of DIBAH was omitted. After 20.0 minutes from its commencement,the polymerization reaction was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. No polymer product was present in themixture. Comparing Example 9 in Table 3 to Comparative Example 15 inTable 4, an organoaluminum compound (e.g., DIBAH) other than analuminoxane is necessary for a polymerization to occur.

Example 16 (Comparative Example)

The same procedure as used in Example 9 was used except that theaddition of MAO was omitted. After 20.0 minutes from its commencement,the polymerization reaction was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. A polymer was not isolated from thepolymerization reaction. Comparing Example 9 in Table 3 to ComparativeExample 16 in Table 4, MAO is necessary for a polymerization to occur.

Example 17 (Comparative Example)

The same procedure as used in Example 11 was used except that theaddition of DIBAH was omitted. After 20.0 minutes from its commencement,the polymerization reaction was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. No polymer product was present in themixture. Comparing Example 11 in Table 3 to Comparative Example 17 inTable 4, an organoaluminum compound (e.g., DIBAH) other than analuminoxane is necessary for a polymerization to occur.

Example 18 (Comparative Example)

The same procedure as used in Example 11 was used except that theaddition of MAO was omitted. After 20.0 minutes from its commencement,the polymerization was immediately terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 3.4 g (0.3% conversion). The resultingpolymer had the following properties: ML₁₊₄=appeared to be very low andwas not measured, M_(n)=72,000, M_(w)=484,000, M_(w)/M_(n)=6.7, cis1,4-linkage content=99.0%, trans 1,4-linkage content=0.5%, and1,2-linkage content=0.5%.

TABLE 4 Comparing Bulk Polymerizations Conducted with and without MAOand DIBAH. Example 13 14 15 16 17 18 Nd/100 g Bd (mmol) 0.006 0.0060.006 0.006 0.006 0.006 NdV/MAO/DIBAH/halide 1/100/0/1 1/0/36/11/100/0/2 1/0/36/2 1/100/0/1 1/0/44/1 Bu₂O/Nd 40/1 40/1 40/1 40/1 40/140/1 Halide CBr₄ CBr₄ t-BuBr t-BuBr Br₂ Br₂ Gel Formation no no no no nono Percent Conversion 0.0  3.4 0.0  0.0  0.0  0.3 ML₁₊₄ — 26.8 — — —very low Mn (kg/mol) — 71 — — — 72 Mw (kg/mol) — 499 — — — 484 MWD — 7.0— — — 6.7 % Cis — 99.0 — — — 99.0 % Trans — 0.6 — — — 0.5 % Vinyl — 0.4— — — 0.5

Comparing Example 11 in Table 3 to Comparative Example 18 in Table 4,MAO is necessary for a polymerization to occur with a conversion over10%, cis 1,4-linkage content above 99.0%, and a narrow molecular weightdistribution.

Example 19

The same procedure as used in Example 1 was used except that 4.7 ml of apremixed 0.0083 M carbon tetrabromide and 0.011 M iodoform (CHI₃) inhexane solution was added instead of CBr₄. After 4.0 minutes from itscommencement, the polymerization was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 165.0 g (12.7% conversion). The resultingpolymer had the following properties: ML₁₊₄=22.3, M_(n)=128,000,M_(w)=219,000, M_(w)/M_(n)=1.7, cis 1,4-linkage content=99.1%, trans1,4-linkage content=0.7%, and 1,2-linkage content=0.2%.

Example 20 (Comparative Example)

The same procedure as used in Example 1 was used except that 2.81 ml of1.0 M DIBAH in hexane was added. After 2.8 minutes from itscommencement, the polymerization was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 130.7 g (10.0% conversion). The resultingpolymer had the following properties: ML₁₊₄=22.1, M_(n)=110,000,M_(w)=269,000, M_(w)/M_(n)=2.4, cis 1,4-linkage content=99.3%, trans1,4-linkage content=0.6%, and 1,2-linkage content=0.1%.

Comparing Example 19 to Comparative Example 20 in Table 5, the mixedbromide-iodide catalyst yielded a polymer with cis 1,4-linkage contentabove 99.0% with a narrower molecular weight distribution than the CBr₄catalyst. The mixed bromide-iodide catalyst had a slower, more desirablerate than the CBr₄ catalyst.

Example 21 (Comparative Example)

The same procedure as used in Example 1 was used except that 2.34 ml of1.0 M DIBAH in hexane was added followed by the addition 6.24 mL of 0.17M CHI₃ in hexane instead of CBr₄. After 5.0 minutes from itscommencement, the polymerization was terminated by diluting thepolymerization mixture with 1360 g of hexane and dropping the batch to 3gallons of isopropanol containing 5 g of2,6-di-tert-butyl-4-methylphenol. The coagulated polymer was drum-dried.The yield of the polymer was 199.4 g (15.4% conversion). The resultingpolymer had the following properties: ML₁₊₄=19.5, M_(n)=148,000,M_(w)=194,000, M_(w)/M_(n)=1.3, cis 1,4-linkage content=98.8%, trans1,4-linkage content=0.9%, and 1,2-linkage content=0.3%.

Comparing Example 19 to Comparative Example 21 in Table 5, the mixedbromide-iodide catalyst yielded a polymer with higher cis 1,4-linkagecontent (above 99.0%) while maintaining a narrow molecular weightdistribution with the slower rate of the CHI₃ catalyst.

TABLE 5 Results from the Mixed Bromide and Iodide Catalyst. Example 1920 21 Nd/100 g Bd (mmol) 0.006 0.006 0.006 NdV/MAO/DIBAH/Bromide*/1/100/36/2/2 1/100/36/4/0 1/100/30/0/4 Iodide* Bu₂O/Nd 40/1 40/1 40/1Bromide CBr₄ CBr₄ — Iodide CHI₃ — CHI₃ Polymerization Rate (g/min) 41.346.7 39.9 Percent Conversion 12.7 10.0 15.4 ML₁₊₄ 22.3 22.1 19.5 Mn(kg/mol) 128 110 148 Mw (kg/mol) 219 269 194 MWD 1.7 2.4 1.3 % Cis 99.199.3 98.8 % Trans 0.7 0.6 0.9 % Vinyl 0.2 0.1 0.3 *halide concentrationis based on the concentration of Br and I, and not on the concentrationof CBr₄ or CHI₃, respectively.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A process for preparing a polydiene, the process comprising the stepof: polymerizing conjugated diene monomer in the presence of adihydrocarbyl ether, where said step of polymerizing takes place withina polymerization mixture that includes less than 20% by weight oforganic solvent based on the total weight of the polymerization mixture,and where said step of polymerizing employs a lanthanide-based catalystsystem that includes the combination of or reaction product ofingredients including (a) a lanthanide compound, (b) an aluminoxane, (c)an organoaluminum compound other than an aluminoxane, and (d) abromine-containing compound selected from the group consisting ofelemental bromine, bromine-containing mixed halogens, and organicbromides, to thereby produce a polydiene having a cis-1,4 linkagecontent in excess of 99%.
 2. The process of claim 1, where thedihydrocarbyl ether is defined by the formula R—O—R, where each R isindependently a hydrocarbyl group or substituted hydrocarbyl groupselected from the group consisting of alkyl, cycloalkyl, substitutedcycloalkyl, alkenyl, and cycloalkenyl groups.
 3. The process of claim 2,where the dihydrocarbyl ether is selected from the group consisting ofdimethyl ether, diethyl ether, di-n-propyl ether, diisopropyl ether,di-n-butyl ether, diisobutyl ether, di-t-butyl ether, di-n-pentyl ether,diisopentyl ether, dineopentyl ether, di-n-hexyl ether, di-n-heptylether, di-2-ethylhexyl ether, di-n-octyl ether, di-n-nonyl ether,di-n-decyl ether, and dibenzyl ether.
 4. The process of claim 3, wherethe dihydrocarbyl ether is selected from the group consisting ofdimethyl ether, diethyl ether, di-n-propyl ether, diisopropyl ether,di-n-butyl ether, diisobutyl ether, di-t-butyl ether, di-n-pentyl ether,diisopentyl ether, dineopentyl ether, di-n-hexyl ether, di-n-heptylether, di-2-ethylhexyl ether, di-n-octyl ether, di-n-nonyl ether, anddi-n-decyl ether.
 5. The process of claim 2, where the organoaluminumcompound other than an aluminoxane is defined by the formulaAlR_(n)X_(3-n), where each R, which may be the same or different, is amono-valent organic group that is attached to the aluminum atom via acarbon atom, where each X, which may be the same or different, is ahydrogen atom, a halogen atom, a carboxylate group, an alkoxide group,or an aryloxide group, and where n is an integer of 1 to
 3. 6. Theprocess of claim 1, where the organic bromides are defined by theformula R_(4-x)CBr_(x), where x is an integer from 1 to 4, and each R isindividually selected from the group consisting of a monovalent organicgroup, a hydrogen atom, and a halogen atom.
 7. The process of claim 2,where the bromine-containing compound is an organic bromide selectedfrom the group consisting of brominated hydrocarbons, acyl bromides, andbrominated carboxylic esters.
 8. The process of claim 2, where thelanthanide-based catalyst system includes the combination of or reactionproduct of ingredients including the lanthanide compound, thealuminoxane, the organoaluminum compound other than an aluminoxane, thebromine-containing compound, and an iodine-containing compound.
 9. Theprocess of claim 8, where the iodine-containing compound is selectedfrom the group consisting of elemental iodine, iodine-containing mixedhalogens, hydrogen iodide, organic iodides, inorganic iodides, metalliciodides, and organometallic iodides.
 10. The process of claim 2, wherethe molar ratio of the aluminoxane to the lanthanide compound is fromabout 5:1 to about 1000:1, the molar ratio of the organoaluminumcompound other than an aluminoxane to the lanthanide compound is fromabout 1:1 to about 200:1, the molar ratio of the bromine-containingcompound to the lanthanide compound is from about 0.5:1 to about 20:1,and the molar ratio of the dihydrocarbyl ether to the lanthanidecompound is from about 0.5:1 to about 1000:1.
 11. The process of claim8, where the molar ratio of iodine atoms in the iodine-containingcompounds to bromine atoms in the bromine-containing compounds is fromabout 0.1:1 to about 10:1.
 12. The process of claim 2, where said stepof polymerizing takes place within a polymerization mixture that issubstantially devoid of organic solvent.